For "portfel" in genitive (dopełniacz) both forms "portfela" and "portfelu" are correct, but "portfela" is more used (frankly, before I have checked in the dictionary, I did not even know that "portfelu" is also correct). Both "hotel" and "portfel" have forms of male declension type I , which has normally an ending -a in genitive singular, so the ending -u is an exception from the rule. The models of Polish declension and conjunction are listed here.
You may easily check forms of polish words in wiktionary: https://pl.wiktionary.org/wiki/portfel#pl and https://pl.wiktionary.org/wiki/hotel#pl - however, I do not trust wiktionary in 100% because I have found also wrong forms there. So you may like to check words in more official dictionary by PWN - see "portfel" , "hotel" - there are also links to scans from old, but a very good dictionary by prof. Doroszewski, containing detailed explanations about usage of words.
Disclaimer: I am not a linguist. I have checked however some dictionaries and I have found that there is a group of male nouns that in Genitive have ending -a, another with ending -u. There are some words which have two or more meanings with the same spelling, and one of them has form with -a, another with -u, and there are also some words with both endings allowed.
"bal - bala" [wooden log], "model - modela" [a person working as a model], "wróbel - wróbla" [sparrow], "sopel - sopla" [icicle], "pal - pala" [post, pile], "skobel - skobla" [peg, wedge; staple], "knedel - knedla" [dumpling], "daktyl - daktyla" [date; dactyl], "cyrkiel - cyrkla" [compass], "węgiel - węgla" [carbon; coal], "kowal - kowala" [blacksmith], "konsul - konsula" [consul], "decyl - decyla" [decile], "dyl - dyla" [timber; joist], "goryl - goryla" [gorilla; bodyguard], "król - króla" [king], "robal - robala" [worm, creepy-crawly], "szakal - szakala" [jackal], "hufnal - hufnala" [haufnagel, a type of nail], "mól - mola" [moth], "debil - debila" [moron], "ul - ula" [hive], "Wasyl - Wasyla" [a first name], "Moskal - Moskala" [Russian or inhabitant of Moscow (old pejorative)], "Kisiel - Kisiela" [the pen-name of a Polish author].
"bal - balu" [ball, party], "model - modelu" [pattern; a type of (car, dress); maquette], "ból - bólu" [pain, ache], "hotel - hotelu", "tiul - tiulu" [tulle, a type of fabric], "perkal - perlaku" [percale, a type of fabric], "skandal - skandalu" [scandal], "szwindel - szwindlu" [swindle], "handel - handlu" [trade, commerce], "cel - celu" [aim, end], "styl - stylu" [style], "trotyl - trotylu" [TNT], "perl - perlu" [font size 5 pt], "westybul - westybulu" [vestibule, lobby], "medal - medalu", "krochmal - krochmalu" [starch; amylum], "symbol - symbolu", "lokal - lokalu" [apartment, office space; club], "nikiel - niklu" [nickel], "azyl - azylu" [asylum], "rubel - rubla" [rouble], "portal - portalu" [portail], "kisiel - kisielu" [a jelly-type dessert].
"portfel - portfela/portfelu" [wallet], "żurnal - żurnalu/żurnala" [journal, magazine], "bajzel - bajzla/bajzlu" [mess], "dzięgiel - dzięgla/dzięglu/dzięgielu" [angelica, a plant]
I do not know why it is so. I have found however, that the declension model we presently use in Polish (worked out by prof. Jan Tokarski), which has 17 types of declension (5 male, 6 female, 6 neutral) is somewhat general and has some exceptions. But there are also other models of declension. Some of them are more detailed - on this page you can find a detailed specification of 146 types of declension (some of which have also numerous subtypes), with sample words (you can browse the exhausive list here and associated tables of declension are accessible from here ).
I have found, that many dictionaries treat ending -a in Genitive as basic form and they include special note only about ending -u (as if it was treated as an exception from the rule) - rarely the other way. However, I did not find a male living noun with ending -u in Genitive - for persons, animals it was always -a.
I have found, that the Pons dictionary informs about form of Genitive in singular and plural, so you may like to use it - f.ex. model - but not for all of them - f.ex. portfel gives only the form of plural Genitive. In all doubt, as previoisly mentionned, I suggest using PWN Dictionary - the free version is already very good, but just to check, I have bought one day access to paid PWN Universal Dictionary - and it is even better, it contains about 100.000 entries, gives a full list of all meanings of given word, with notes on declension and respective synonyms, antonyms and associated words, with samples of use and proverbs. Just to inform - PWN is formally only a Publishing House, but due to its specialisation and close cooperation with Rada Języka Polskiego (The Polish Language Authority), their publications may be treated as standardization of the Polish language.
I have found also, that Genitive case in nowadays Polish serves also function of non existing anymore Ablative case (preserved only in some old proverbs, f.ex. "Gość nie w porę gorszy Tatarzyna" - Tatarzyna ablative case = od Tatarzyna genitive case), and perhaps this explains why there are so often various forms just for the Genitive case - some may be coming from old Genitive, some from old Ablative.
Therefore, I would say, that using "hotel" as the model of inflection of polish male nouns is not wrong - but incomplete. You should remember that for both singular and plural Genitive, there are 2 variants. This guide over the 17 main types of declension suggests "kowal"/"król" for living male nouns, and "pal"/"bal" for non-living male nouns - but as you see above, in some cases it may be hard to guess which declension is right, so you probably have to check it always.
If you want me to dig deeper, I should probably ask someone - my old aunt has a friend, a retired teacher of Polish language, I could ask her for some help.
I think you do not need to bother about the long list - you may easily treat it as an exhaustive list of exceptions or a reference in dubious cases. It is enough just to know that such a list exists. They do not teach it at school - only the 17 types, mentioning only about some exceptions, to be checked in need, in a dictionary.
Many of the words on the long list are just family names you will never use - or the owner will tell you how to inflect his name. Many are ancient words you will never even know. I am over 40, have spent more than 90% of my life in Poland, have read thousands of books in Polish and did not even know, that a word "abbuś" exists in Polish. What is a "fontaź"? - ah, it was used in 17 and 18 century. What is a "gzło"? Ah, it is a 11-12 century form of "giezło", but even "giezło" was used maybe in 14-16 century. I might have seen "bargiel" once or twice, and did not even remember what is it (another name of "kowalik", a bird species).
So, do not cry ;-) It is not so bad as it seems.
Don't bother learning all the billions of different declension types. Part of learning a language is finding a good balance between memorizing and absorbing through practice. Pick one, maybe two common declension tables, and learn those off by heart. Apply them indiscriminately to all nouns as though there were no irregular nouns. You'll be correct 60 to 80% of the time, and the rest of the time make mistakes that probably won't prevent you from being understood. You'll learn the irregular nouns as you go along.
Become fluent first, then you can start worrying about irregular nouns.
Because it's not. Somewhere there's a pole wondering why in english we don't say "I'm looking my wallet" instead of "I'm looking for my wallet". Same answer: the verb just doesn't work that way.
(Actually I'm not a native speaker so maybe you can say "szukam dla", but the point still stands: don't think too hard about when to use what prepositions. It's ultimately arbitrary and handled on a verb-by-verb basis).
The distinction that you noticed exists in Accusative (biernik), but in Genitive (dopełniacz) all the male nouns go with the same form of possessive pronoun. The full declension list of this pronoun is here. The types of nouns used in these tables can be found here, but they are not clearly listed, so I did it for you:
- m1 - male human
- m2 - male non-human animated (mainly animals, but it works also with many vegetables)
- m3 - male inamimated
- ż - female
- n1 - neuter, connecting collective numerals (dwoje, pięcioro) - only few nouns, e.g.: dziecko (child), oko (eye), ucho (ear)
- n2 - neuter, connecting cardinal numerals (dwa, pięć)
- p1 - personal
- m1 - male human
- ndepr - non-depreciative (regular) form
- depr - depreciative form
- p2 - non-personal, capable of connecting numerlas
- p3 - non-personal, incapable of connecting numerlas
- pozostałe - others
This distinction in Accusative exists also for some other pronouns, see e.g.: the tables here.
The verb "widzieć" (see) takes accusative, so:
- Widzę mojego meża - I can see my husband
- Widzę mój portfel - I can see my wallet
But when any verb is negated it always takes genitive, therefore:
- Nie widzę mojego meża - I can't see my husband
- Nie widzę mojego portfela - I can't see my wallet
Look here for the use of genitive case in Polish
If you mean a small purse, just for holding the money, 1 or 2 credit cards and sometimes an ID card - it is "portmonetka". If you mean a bigger purse, in which a woman can hold all the stuff she needs, it is "torebka": https://dictionary.cambridge.org/dictionary/english-polish/purse_1 See: